Panoramic shot of GG 3.0, the third iteration of General Graphene’s proprietary industrial-scale CVD graphene production system.
Graphene’s Relationship with Polymers
Graphene has been frequently discussed in relation to polymers ever since it was discovered in 2004. The incorporation of graphene into polymers and the resulting end application is dependent on several factors – such as the type of graphene, the polymer substrate used, and the graphene production technique used, to name a few.
Chemical vapor deposition (CVD) graphene is a one-atom thick carbon layer typically grown on the surface of a metallic catalyst material – with copper being one of the most common growth substrates used for monolayer CVD graphene growth. CVD graphene transfer has proved to be an essential manufacturing step for its use in certain applications (Bahri et al., 2021) and when it comes to polymers, in most cases, a transfer step is required.
Owing to CVD graphene’s substrate-dependent behavior, the underlying polymer plays a crucial role in determining the various properties – such as thermal or electrical – of the resulting CVD graphene polymer composite. Typically, a chemically and thermally stable polymer that does not indirectly dope CVD graphene is desirable to harness the properties of CVD graphene when incorporated into a polymer. CVD graphene polymer composites can be used as conductive coatings, sensing elements, and to develop various flexible electronic devices.
The Challenges of CVD Graphene Transfer
Despite advances in CVD graphene transfer across the industry, there are several challenges that have been obstacles towards achieving a scalable process for large-area CVD graphene transfer. These include – batch scale limitations, the difficulty of obtaining largely contaminant-free CVD graphene, high operating and input costs, the use of harsh chemicals, and the introduction of defects in the CVD graphene surface because of transfer-induced tears (Chen et al., 2016). The most common transfer methods used for CVD graphene are oxidative decoupling and wet etch transfer – which are batch scale processes that have been tested in a roll-to-roll format. However, both these processes are time consuming and chemically intensive to implement in a roll-to-roll format, thereby making it challenging and expensive to scale them.
While transfer-free or direct growth production methods have been discussed widely to mitigate the challenges of CVD graphene transfer, the primary bottleneck is that CVD graphene can only be grown directly on certain catalytic substrates. Direct growth of CVD graphene on silicon, for example, is hampered by poor crystal quality and the requirement of a high growth temperature (Avishan et al., 2021).
Advancements in Roll-to-Roll CVD Graphene Transfer
Outfeed view of General Graphene’s proprietary Roll-to-Roll CVD Graphene Transfer system.
Roll-to-roll transfer remains the goal of most companies manufacturing CVD graphene, but most have found the technique difficult to scale and perfect. General Graphene has made several advancements in both its roll-to-roll CVD graphene production and transfer technologies to directly address the challenges of producing mass volumes of CVD graphene films cost-effectively at reproducible qualities tailored for specific end applications.
Towards the end of 2022, General Graphene completed the integration of an inline coating system to GG 3.0, the third iteration of its proprietary roll-to-roll chemical vapor deposition (CVD) production system. This integrated system enables General Graphene to coat a variety of thin polymer films onto a roll of CVD graphene-on-catalyst substrate. The thin polymer film coatings can also be cured and laminated before the resulting graphene-on-polymer output leaves the GG 3.0 production. The output is fed directly into General Graphene’s Roll-to-Roll CVD Graphene Transfer system where the graphene-on-polymer is separated from the surface of the catalyst material.
General Graphene’s Roll-to-Roll CVD Graphene Transfer system has successfully been used to transfer several tens of square meters of roll-to-roll CVD graphene on polymers and can transfer several hundreds of square meters of roll-to-roll CVD graphene on polymers. Additionally, this system has a very small chemical footprint which thereby makes it easier and less expensive to implement at scale.
General Graphene is also able to successfully reuse copper foil – its primary catalyst material – once the graphene-on-polymer has been separated from it. The ability to reuse the catalyst material has been mentioned as a key driver towards enabling scalable CVD graphene mass production (Bahri et al., 2021) and General Graphene’s advancements in this area have played a crucial role in driving its direct production cost between 2 to 3 orders of magnitude below the industry standard.
The Impact of Large-Area CVD Graphene Polymer Composites
At General Graphene, we have always held the belief that human beings were never meant to handle nanoscale materials. This belief has been the primary driver in our efforts to automate CVD graphene transfer in a way that allows for large-area, minimal defect, low chemical footprint, roll-to-roll transfer of CVD graphene.
Both our CVD graphene production and transfer systems have been configured to support the development of large-area roll-to-roll CVD graphene films on a variety of polymers such as PMMA, EVA, PI, to name a few. General Graphene’s advancements in the roll-to-roll synthesis and transfer of CVD graphene represents an unprecedented breakthrough and paves the way for the development of CVD graphene polymer composites in mass volumes and at a low cost. To provide some context, the per unit cost of using CVD graphene on a polymer compatible with a sensor application has gone from a few dollars to a fraction of a dollar – representing a paradigm shift in the commercialization of CVD graphene polymer composites.
Avishan N, Hussain N, Nosheen F (2021) Large-scale Graphene Production and Transfer for Industrial Applications. Materials Innovations 2 (1), 15-25.
Bahri, Mohamed & Shi, Biao & Khouloud, Djebbi & Elaguech, Mohamed Amin & Zhou, Daming & Ali, Mounir & Tlili, Chaker & Wang, Deqiang. (2021). Toward clean and crackless polymer-assisted transfer of CVD-grown graphene and its recent advances in GFET-based biosensors. Materials Today Chemistry. 22. 10.1016/j.mtchem.2021.100578
Chen, Gong, X., & Gai, J. (2016). Progress and Challenges in Transfer of Large‐Area Graphene Films. Advanced Science, 3(8), 1500343–n/a. https://doi.org/10.1002/advs.201500343